Lens
and the sensitive plate, and Mr. Dallmeyer supplies these negative lenses so as to work either with ordinary doublets or portrait lenses - thus it does not become necessary for the tourist, in all cases, to take with him a complete telephotographic combination in addition to his ordinary lenses. For securing instantaneous pictures of distant or shy animals, however, it-is very desirable to use the telephotographic system in which a portrait lens is the positive combination; and with this some very remarkable pictures of birds and other easily frightened animals have been secured. The Dallmeyer M Stigmatic " lens (fig. 98) is a portrait combination, which appears to have all the advantages, and perhaps more, than the older construction to which the astigmatic corrector is adapted. At the full aperture,
![]() ![]() but limited uses, owing to. that lack of depth of focus which is intrinsically inherent to such an aperture; but to the professional photographer, or one wishing to obtain studies of animal life, the stigmatic lens gives new powers. The defining power of the stigmatic lens may be reduced by a provision for disturbing the correction of spherical aberration, in which case it gives a uniform softness all over the field. The above remarks apply especially to the stigmatic lens in its original form and working at
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